The SandboxLink extension adds a link to a personal sandbox, within the personal tools menu. The target is the "/sandbox" subpage of the user's user page.

The label of the link and the page name are taken from system messages and can be translated at

Wiki administrators can configure the sandbox page name and preload and editintro URL parameters by editing system messages, as explained at Extension:SandboxLink#On-wiki configuration.

To disable this feature for yourself, add #pt-sandbox { display: none; } to your personal CSS page: Special:MyPage/common.css